Attempts to map out distinct microenvironments of organized biological molecules and aggregates such as proteins, polynucleotides and membranes have been the subject of intensive recent research. Fluorescent probes have been effectively employed as a means of investigating the structure and dynamics of such systems. The general idea behind such probes is that a molecule, whose fluroscence is sensitive to its microenvironment, will (a) display a specific affinity for a given site (e.g., the interior of a micelle, or the active side of an enzyme relative to bulk solution) and (b) possess measurably distinct fluorescence properties which uniquely characterize the various environments. We propose to investigate the structure and dynamics of micelles by the use of fluorescence probes, to expand the general luminescent probes to include phosphorescent and chemiluminescent probes and to extend the idea of luminescent probes to include photochemical probes. Some major objectives of this work are to utilize luminescent and photochemical probes to elucidate the factors which determine the association and dissociation rates of micellar aggregates, to measure these rates quantitatively, to elucidate the factors which control the motion of solubilized molecule across a micelle boundary and to measure these rates quantitatively. The major method to be employed is time and frequency resolved single photon counting + stopped-flow spectrophotometry. We propose to develop our initial encouraging results on phosphorescent and chemiluminescent probes for study of micellar structure and dynamics. We also will seek to develop methods to "flash generate" detergent molecules and oxygen molecules. Should these studies be successful a new and powerful method for elucidating dynamics of micellar, bilayer and membrane systems would become available. Finally, we propose to investigate the mechanism of photosensitized cleavage of thymine dimers in micellar system. It is hoped that these results will be relevant as a model for interpreting the action of photoreactivating enzymes which repair photodamaged DNA.